[geebow]

I have some large ballscrew linear actuators. The nominal power is 400W and 200V 10mm per rev, 3000rpm nominal max speed. The controllers that came with them were point to point positioners only. Pushing the actuator carriage and scoping the windings tells me they are 8 pole 3 phase ac servo motors (200Hz), 78Vrms back emf phase to phase at nominal max speed.

I want to be able to control tool trajectory in multiple axes so a digital speed controller loop nested inside contnuous positioning control loop would be ideal. But alas the budget, she is small. So a pulse train input servo controller will probably be my next best thing, provided I can tune the internal PID loop well.

The linear actuator encoder is a 17 bit absolute tamagawa brand. I can get pulse train position input versions of these servo drives (Yaskawa SGD/SGDA sigma I, or Omron R88D-UPxxxxx) to match the voltage and wattage of my actuators. I will need to generate my own A,/A,B,/B 5V quadrature @2048 PPR (Not hard so far). But information about the S,/S encoder channel is proving to be beyond my grasp. So I am throwing myself on to the mercy of any of the yaskawa experts out there. Please help a newbie/tryo out.

As I understand it the S channel on these yaskawa motors provides armature position for motor winding commutation indexing by changing duty cycle between 25% and 75%, and on an 8 pole motor (which I think the 3000rpm yaskawas are) will change through the full range 4 time per rev.

Questions for experts;
Q1 Are the yaskawa sigma 1 drives nominal 200hz output and their 3000 rpm motors 8 poles?
Q2 When we talk about the nominal emf for AC servos, what do we mean. Is it the DC bus voltage?
Q3 Can anybody tell me about or point me to the S channel details. How are the change points aligned with the armature pole positions? Is it a step change from 25% to 50% to 75%, or a steady continuous change? Is it a continuous pulse stream, electronically generated within the encoder so that it can generagte a pulse stream even at standstill?

I guess if I have to I can go out and buy a matching motor and characterise it that way. But like I said, the budget she is small. If anybody has, (or knows where to get one) an Omron R88D-U40030V motor or Yaskawa SGM/SGMS (400w, 3000rpm, incremental encoder)equivalent for sale at the right price let me know.

Thanks in advance

[mactec54]

Hi geebow

I see the first problem you will have to deal with is the 17bit encoder the drives that you want to use will not work with the 17bit encoder, if you change your motor for a SGM/ SGMP/ SGMG you will be fine they have the 2048 incremental encoder you need for those drives, just make sure that the motors you get do have the 2048 encoder as they do come with some different encoders

Don't worry about the other tec stuff in your post, Just down load the Manual from the Yaskawa site for the SGDA & SGM drives/motors & you will have all you need to know to get them running

[geebow]

Thanks for that Mactec. Re powering the linear actuator was always an option. But these actuators are soooo nice. All integrated motor and encoder behind a very clever dust exclusion system. They are the IA brand ISDL (D for dust proof, L for large), very strong and stiff 800mm travel with 1 carriage, 600mm with the two carriages fitted. I am tempted to try and use these existing integrated motors, at least untill I run into an absolute dead end.

I have found a motor in HongKong and made an offer. I'll try and spin it in a lathe to characterise the encoder 3rd channel. May take a while but will post results if successful.

And when that all ends in tears, I'll rip off the existing AC servo PM rotor and hook up an external motor! Probably another 6 months down the track. Ah well that's how these projects go.

[mactec54]

geebow

You should try ebay they always have the SGM motors on there 400w 200v Just type in Yaskawa, They most of the time have 10 pages, from new to used never pay more than a $100 new for that motor